Controlling Access to Program Usage Data

ABSTRACT

A television program ratings method and system includes transferring information associated with households from a cable provider to a ratings provider such that the ratings provider has access to information associated with sampled households and lacks access to information associated with non-sampled households. To this end, identity information and usage information associated with the households are respectively anonymized and encrypted. Knowledge of the identities of the sampled households enables the anonymized identity information and the encrypted usage information for the sampled households to be respectively de-anonymized and decrypted. The ratings provider knows which households are sampled households. As such, the ratings provider de-anonymizes and decrypts the information associated with the sampled households and then uses the de-anonymized and decrypted information to determine television program ratings. The cable provider anonymizes and encrypts the information for all households as the cable provider does not know which households are sampled households.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 16/382,934, filedApr. 12, 2019, now allowed, which is a continuation of U.S. applicationSer. No. 15/728,590, filed Oct. 10, 2017, now U.S. Pat. No. 10,264,316,issued on Apr. 16, 2019, which is a continuation of U.S. applicationSer. No. 14/991,574, filed Jan. 8, 2016, now U.S. Pat. No. 9,826,271,issued on Nov. 21, 2017, which is a continuation of U.S. applicationSer. No. 14/028,010, filed Sep. 16, 2013, now U.S. Pat. No. 9,277,291issued on Mar. 1, 2016, which is a continuation of U.S. application Ser.No. 13/097,738, filed Apr. 29, 2011, now U.S. Pat. No. 8,561,094 issuedon Oct. 15, 2013, which is a continuation of U.S. application Ser. No.12/641,923, filed Dec. 18, 2009, now U.S. Pat. No. 7,958,523 issued onJun. 7, 2011, which is a continuation of U.S. application Ser. No.11/041,655, filed Jan. 24, 2005, now U.S. Pat. No. 7,653,920 issued onJan. 26, 2010, the disclosures of which are all hereby incorporated byreference in their entireties.

TECHNICAL FIELD

The present application generally relates to the field of televisionprogram ratings and, more particularly, to a method and system fortransferring cable television subscriber information to a televisionprogram ratings provider such that the ratings provider has access tothe information of sampled cable television subscribers while beingprevented from accessing the information of the remaining cabletelevision subscribers.

BACKGROUND

A television program rating is a measure of the number of viewerswatching a television program. Television program ratings are importantfor determining advertising revenue which can be charged for programs.Demographic analysis of rating information is important because programsintended for children desirably include advertisements for items ofinterest to children such as toys, while programs intended for adultsdesirably include advertisements for items of interest to adults such asautomobiles and household products.

A cable television subscriber household generally includes one or moretelevisions with each television being associated with a cable networkdevice such as a set-top-box (STB). STBs connect associated televisionsto the network infrastructure of a cable television service provider. ASTB provides programs received from the cable provider to the associatedtelevision for household members to view. A household member selects achannel using the STB and then the television receives programsassociated with the selected channel from the cable provider via theSTB.

Household members also provide Video-on-Demand (VOD) commands to the STBfor receipt by the cable provider. VOD generally refers to a head-endbased transmission of content from the cable provider to the householdsupon requests from the household members. A household member provides aVOD command to the STB in order to request that the cable providerdeliver a program to the STB for viewing on the television. In thiscase, the STB transfers the VOD command to the cable provider which inturn provides the desired program to the STB for display on thetelevision. VOD has transport controls like a video cassette recorder(VCR). VCR-type VOD commands enable household members to view programson their own schedules. Such VOD commands include play, pause, fastforward, rewind, playback, etc. The cable provider controls programsdisplayed on the television accordingly in response to these VODcommands.

A method of collecting viewing data from a cable television subscriberhousehold to determine program ratings includes connecting a monitor toeach STB in the household. The monitor detects the channel to which theassociated television is tuned and when each tune takes place. Themonitor may also be configured to prompt a household member to identifyhim or herself as part of a program audience. The monitor provides theviewing data to a central office for use by a television program ratingsprovider. The ratings provider compares the viewing data with referencedata which includes a list of programs available on each channel duringgiven times. By comparing the tuned channels, i.e., the channels towhich the television is tuned, to the programs available on thosechannels at the time, the ratings provider can determine the programsviewed by household members.

This viewing data collection method is performed on a sampledcross-section of households in a viewing area. The ratings provider usesthe viewing data from the sampled households to determine programratings. The sampled households are a subset of all households in theviewing area. The sampled households are chosen using methodologicalstandards such that the subset represents the viewing behavior of allhouseholds in the viewing area. Typically, the sampled households haveagreed to allow collection and use of their private viewing information.

Cable providers have expanded their pay-per-view (PPV) services intoother areas of On-Demand and are using new digital compressiontechnologies for distribution. As a result, a problem with the describedviewing data collection method is that simply knowing channel positionsand channel change times does not provide sufficient informationregarding actual demand events that have been viewed.

A solution is to collect VOD usage data from the sampled households forthe ratings provider to use in order to determine program ratings. VODusage data of a household is indicative of programs and other VOD eventsthat have been viewed by household members. The cable provider logs suchVOD usage data as the cable provider streams programs to the STBs in thehouseholds. Thus, the ratings provider could obtain the VOD usage datafor the sampled households from the cable provider to determine programratings.

However, policies and regulations mandate that personally identifiableinformation be protected from scrutiny by unauthorized third parties.Anonymous information may be tracked and analyzed, but anonymousinformation provides reduced value because anonymity obscures links todemographic information. Sampling methods where certain sub-populationsopt in and allow their usage to be tracked (i.e., the sampled householdsin a viewing area) provide the required demographic information, but tomaintain statistical sample properties the identities of the subsetwithin the larger population (i.e., all households in the viewing area)must remain anonymous. This complicates data collection from withinlarger data samples where household-specific identifying information ismade anonymous.

Thus, a problem with the above-described solution of having the ratingsprovider obtain the VOD usage data for the sampled households from thecable provider is that the ratings provider has to keep private thesampled household identities. As such, the cable provider does not knowthe identities of the sampled households. Thus, to overcome thisproblem, the cable provider has to provide the ratings provider with theVOD usage data for all households in order for the ratings provider tohave the VOD usage data for the sampled households.

However, a problem with this solution is that the ratings provider isnot authorized to know the non-sampled household identities. Further,the cable provider does not want to provide the ratings provider withthe VOD usage data of the non-sampled households as the ratings provideris not entitled to this information. Thus, the ratings provider isauthorized to access the information (identity and VOD usage date)associated with the sampled households but is not authorized to accesssuch information associated with the non-sampled households.

In sum, the ratings provider knows the sampled household identities. Thecable provider has the information associated with all households in theviewing area. The ratings provider is authorized to obtain theinformation associated with the sampled households from the cableprovider, but cannot tell the cable provider the sampled householdidentities. As a result, the cable provider has to provide the ratingsprovider with the information associated with all households in theviewing area in a manner which allows the ratings provider to access theinformation associated with the sampled households and which preventsthe ratings provider from accessing the information associated with thenon-sampled households.

SUMMARY

Accordingly, it is an object of the present invention to provide amethod and system for transferring information associated with cabletelevision subscribers from a cable television service provider to atelevision program ratings provider such that the ratings provider hasaccess to the information associated with sampled subscribers and lacksaccess to the information associated with the remaining non-sampledsubscribers.

It is another object of the present invention to provide a method whichallows efficient selection of a known subset (i.e., sampled householdsin a viewing area) from within a larger population (i.e., all householdsin the viewing area) while maintaining data security for others (i.e.,the remaining non-sampled households in the viewing area).

It is a further object of the present invention to provide a method forthe dissemination of reporting information including a sampling ofsubscribers (i.e., sampled households in a viewing area) within a largerpopulation (i.e., all households in the viewing area) to third parties(i.e., ratings provider) while preserving data security for subscribers(i.e., non-sampled households) that have not opted into the analysisprocesses of these third parties.

It is still another object of the present invention to provide a methodfor transferring identity and VOD information associated with householdsin a viewing area from a cable provider to a ratings provider in whichthe method includes anonymizing the identity information and encryptingthe VOD information prior to transfer to the ratings provider in amanner which allows the ratings provider to de-anonymize and decrypt theinformation associated with sampled households and which prevents theratings provider from de-anonymizing and decrypting the informationassociated with the non-sampled households.

In carrying out the above objects and other objects, the presentinvention provides a method and an associated system for transferringinformation associated with households from a cable provider to aratings provider. The method includes associating a subset of householdswith a ratings provider such that for each household in the subset theratings provider knows identification information indicative of thehousehold. The households in the subset are sampled households and theremaining households in the subset are non-sampled households. Themethod further includes logging information associated with programsstreamed from a cable provider to the sampled and non-sampledhouseholds. The logged information for each program streamed to ahousehold includes identification information indicative of thehousehold receiving the program and usage information indicative of theuse by the household of the program.

A report of the logged information is then generated such that for eachprogram streamed to a household the report includes a record of thelogged information for the program streamed to the household. Theidentification information and the usage information contained in eachrecord in the report are then respectively anonymized and encrypted toanonymize and encrypt the report such that each record in the anonymizedand encrypted report is able to be de-anonymized and decrypted by areceiving party if the receiving party knows the identificationinformation contained in the record. The de-anonymization and decryptionmay require the receiving party to correlate the identificationinformation contained in a record with other information not present inthe record. The anonymized and encrypted report is then transferred fromthe cable provider to the ratings provider. At the ratings provider, theknown identification information indicative of a sampled household isused to de-anonymize the anonymized identification information anddecrypt the encrypted usage information of a record in the anonymizedand encrypted report which corresponds to the sampled household.

The known identification information indicative of the sampledhouseholds may be used to de-anonymize the anonymized identificationinformation and decrypt the encrypted usage information of all recordsin the anonymized and encrypted report which corresponds to the sampledhouseholds. The de-anonymized identification information and thedecrypted usage information of the records corresponding to the sampledhouseholds may then be used by the ratings provider to determine programratings.

The method may further include disallowing the ratings provider fromadvising the cable provider as to the identification information knownby the ratings provider in order to prevent the cable provider fromdetermining which households are sampled households and which householdsare non-sampled households.

In the method, the step of anonymizing and encrypting the report may besuch that each record in the anonymized and encrypted reportcorresponding to a sampled household is able to be de-anonymized anddecrypted by the ratings provider as the ratings provider knows theidentification information contained in the records corresponding to thesampled households. In this case, the step of anonymizing and encryptingthe report may be such that each record in the anonymized and encryptedreport corresponding to a non-sampled household is unable to bede-anonymized and decrypted by the ratings provider as theidentification information contained in the records corresponding to thenon-sampled households is unknown to the ratings provider.

The logged information for each program streamed to a household mayfurther include timing information (e.g., a time stamp) indicative ofthe time at which the household received the program. In this case, thestep of anonymizing and encrypting each record in the report toanonymize and encrypt the report includes leaving the timing informationcontained in the record alone. Further, in this case, afterde-anonymizing the anonymized identification information and prior todecrypting the encrypted usage information of a record in the anonymizedand encrypted report which corresponds to a sampled household, themethod includes filtering out the record corresponding to the sampledhousehold if the time at which the sampled household received a programas indicated by the timing information contained in the record fallsoutside of an eligible time period associated with the sampledhousehold.

Each household preferably includes a cable television network devicesuch as a set-top-box (STB) to enable the cable provider to streamprograms to the household. The identification information for eachhousehold includes an address for the STB in the household. In thiscase, the step of anonymizing and encrypting the report further includesusing the STB addresses associated with the households such that theusage information contained in each record in the report is encryptedusing the STB address associated with the record. The step ofde-anonymizing and decrypting a record in the anonymized and encryptedreport which corresponds to a sampled household includes using the knownSTB address of the sampled household to de-anonymize the anonymizedidentification information and decrypt the encrypted usage informationof the record corresponding to the sampled household.

The step of encrypting the usage information contained in each recordmay be performed such that the STB address included in theidentification information contained in the record is a decryption keyfor the record, or that the decryption key is derived from the STBaddress in part or in whole.

The step of anonymizing and encrypting the report may further includeusing a report key associated with the report such that theidentification information and the usage information contained in eachrecord in the report are respectively anonymized and encrypted using thereport key associated with the report. In this case, the step ofde-anonymizing and decrypting a record in the anonymized and encryptedreport which corresponds to a sampled household includes using the knownSTB address of the sampled household and the report key associated withthe report in order to de-anonymize the anonymized identificationinformation and decrypt the encrypted usage information of the recordcorresponding to the sampled household.

Each household may be associated with an account number. An accountnumber is a specific example of well-known information correlated to theidentification information available to both the cable provider and theratings provider. Such well-known information can be omitted from therecords, yet used in their decryption. As such, the term “accountnumber” as used herein includes other information correlated to theidentification information available to both the cable provider and theratings provider.

The identification information for each household includes the accountnumber associated with the household. In this case, the step ofanonymizing and encrypting the report further includes using the accountnumbers associated with the households such that the usage informationcontained in each record in the report is encrypted using the accountnumber associated with the record. In accordance with a safer encryptionapproach of the present invention, the step of encrypting includesderiving an encryption key from a report key (which may vary perreport), the STB address (contained in the report), and the correlatedaccount number (not the in the report). The step of de-anonymizing anddecrypting a record in the anonymized and encrypted report whichcorresponds to a sampled household includes using the account numberassociated with the record corresponding to the sampled household todecrypt the usage information of the record corresponding to the sampledhousehold. In accordance with the safer encryption approach of thepresent invention, the step of decrypting includes deriving a decryptionkey from the report key, the STB address, and the account number.

The usage information for each program streamed to a household mayinclude Video-On-Demand (VOD) viewing statistic information indicativeof the use by the household of the program. The usage information foreach program streamed to a household may also include provideridentification (PID) information indicative of the provider of theprogram and asset identification (AID) information indicative of theidentity of the program.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of a system for transferringinformation associated with households from a cable television serviceprovider to a television program ratings provider in accordance with thepresent invention;

FIG. 2 illustrates a VOD program stream information report forhouseholds in a viewing area during a given time period, a ratingsprovider information table, and a cable provider information table inaccordance with the present invention;

FIG. 3 illustrates the VOD program stream information report shown inFIG. 2 anonymized and encrypted in accordance with a simpleanonymization and encryption approach of the present invention;

FIG. 4 illustrates the VOD program stream information report shown inFIG. 3 de-anonymized and decrypted in accordance with the simpleanonymization and encryption approach of the present invention;

FIG. 5 illustrates the VOD program stream information report shown inFIG. 2 anonymized and encrypted in accordance with a safer anonymizationand encryption approach of the present invention; and

FIG. 6 illustrates the VOD program stream information report shown inFIG. 2 de-anonymized and decrypted in accordance with the saferanonymization and encryption approach of the present invention.

DETAILED DESCRIPTION

Referring now to FIG. 1, a block diagram of a system 10 for transferringinformation associated with cable television subscriber households 12 a,12 b, 12 n from a cable television service provider 14 to a televisionprogram ratings provider 16 in accordance with the present invention isshown. Households 12 are located in a given viewing area serviced bycable provider 14 and are subscribers of the cable provider. Households12 generally include at least one television having an associatedset-top-box (STB). The STBs connect the associated televisions withcable provider 14 to enable the cable provider to provide households 12with programs for viewing by the household members on the televisions.

The STBs provide programs received from cable provider 14 to theassociated televisions in households 12 for the household members toview. The programs include Video-On-Demand (VOD) programs. Typically, ahousehold member selects a channel using the STB for the associatedtelevision to receive VOD programs associated with the selected channelfrom cable provider 14. While viewing a VOD program on a television, ahousehold member may provide VOD commands to the STB in order to controlthe VOD program. Such VOD commands include play, pause, fast forward(FF), rewind, and the like. Cable provider 14 controls the VOD programsdisplayed on a television in response to the STB associated with thetelevision receiving VOD commands from household members.

Cable provider 14 provides a VOD program to the STB of a household 12 aspart of a data stream. Cable provider 14 logs information regarding VODprogram streams provided to households 12. For each VOD program streamprovided to a STB in a household 12, the logged information includes thefollowing fields of information: (i) STB identification, (ii) the time(e.g., date) at which the VOD program is provided to the STB, (iii) VODprogram identification, and (iv) VOD program usage information. Thisinformation associated with a VOD program stream (i.e., the STBidentification, the date, the VOD program identification, and the VODprogram usage information) is termed as “the VOD program streaminformation” herein.

Cable provider 14 periodically generates reports having logged VODprogram stream information for households 12 in a viewing area. Eachreport includes individual records of the VOD program stream informationlogged for VOD programs provided to STBs within a given time period.That is, each record in the report includes the VOD program streaminformation logged for a VOD program provided from cable provider 14 toa given STB at a given time.

The STB identification can be the media access control (MAC) address ofthe STB receiving a VOD program. The STB MAC address may be used toidentify the household in which the STB is located. Demographicinformation associated with the household may be obtained using thehousehold location information (such as ZIP code). The STB and/or thehousehold are typically associated with an account number which may beable to be obtained based on the STB identification.

The date at which the VOD program is provided to the STB is generallyindicative of the date at which household members view the VOD program.The VOD program identification information includes provider informationwhich identifies the provider of the VOD program, and includes assetinformation which identifies the identity (e.g., title) of the VODprogram.

The VOD program usage information is indicative of VOD aggregate viewingstatistics of a VOD program in a stream. VOD aggregate viewingstatistics include total minutes of play, fast forwarding, and rewindingof a VOD program in a stream as the VOD program is controlled inaccordance with VOD commands.

Ratings provider 16 desires to correlate the viewing statistics withasset metadata in order to determine program ratings for VOD programs.To this end, ratings provider 16 has agreements with certain households12 in the viewing area to access the VOD program stream information forthese households. Such households are termed as “sampled households”herein as these households provide a sampling of all households in theviewing area. The remaining households in the viewing area are termed as“non-sampled households” herein. Typically, ratings provider 16 hasagreements to access the VOD program stream information for sampledhouseholds during certain eligibility time periods. Thus, a householdmay be a sampled household for a given time (such as a given weekday)and then be a non-sampled household for all other times (such as theother days in the week).

It is noted that ratings provider 16 may be an entity independent ofcable provider 14. For example, ratings provider 16 may be a televisionratings program provider such as Nielsen Media Research. Alternatively,ratings provider 16 may be a distinct division of cable provider 14. Forexample, cable provider 14 may include a division responsible fordelivering programs via its cable infrastructure network to thesubscriber households, and include a separate independent division fordetermining television program ratings. Herein, “cable provider” refersto an entity responsible for delivering programs via a cableinfrastructure network to subscriber households and “ratings provider”refers to an entity responsible for analyzing sampled householdinformation to determine program ratings.

As indicated above, cable provider 14 logs the VOD program streaminformation for all households 12 in the viewing area. As such, ratingsprovider 16 has to obtain the VOD program stream information for thesampled households from the cable provider in order to access suchinformation. Ratings provider 16 knows the identities of the sampledhouseholds as the ratings provider has agreements with these householdsto have access to the VOD program stream information associated withthese households. These agreements typically require that ratingsprovider 16 not reveal the identities of the sampled households toanyone else including cable provider 14. Likewise, cable provider 14does not wish to reveal the identities of the non-sampled households toanyone else including ratings provider 16. Further, cable provider 14generally desires that ratings provider 16 does not have access to theviewing statistics for the non-sampled households.

Thus, cable provider 14 has to provide ratings provider 16 with thereports having the VOD program stream information for all households 12in a viewing area in a manner which (i) allows the ratings provider toaccess the VOD program stream information for the sampled households and(ii) prevents the ratings provider from accessing the VOD program streaminformation for the non-sampled households. Cable provider 14 has toprovide ratings provider 16 with the VOD program stream information forall households 12 (sampled and non-sampled) as the cable provider doesnot know the which households are sampled households. That is, cableprovider 14 cannot pre-filter the reports to provide ratings provider 16with the VOD program stream information for just the sampled households.

As indicated above, neither cable provider 14 nor ratings provider 16may reveal the identities of their viewers, e.g., to each other. Theeligibility period in which a household is a sampled household isdefined by start and end times. Ratings provider 16 identifies sampledhouseholds from the STB MAC addresses and also perhaps from the accountnumbers. In order for cable provider 14 to provide ratings provider 16with reports having the VOD program stream information for allhouseholds 12, the cable provider and the ratings provider have to agreeon the correlation of anonymized versions of the reports. As indicatedabove, cable provider 14 cannot pre-filter such reports to remove theVOD program stream information for the non-sampled households as ratingsprovider 16 cannot advise the cable provider of the identities of thesampled households. As such, cable provider 14 has to provide the VODprogram stream information for all households at all times to ratingsprovider 16.

To this end, anonymization and encryption techniques are used on the VODprogram stream information reports in accordance with the presentinvention in order to enable cable provider 14 to transfer the reportsto ratings provider 16 such that the ratings provider (i) has access tothe VOD program stream information for the sampled households and (ii)lacks access to the VOD program stream information for the non-sampledhouseholds.

General anonymization and encryption techniques carried out inaccordance with the present invention in order to provide privacy andsecurity will now be described. A basic understanding of encryption(with cryptographic terms in parentheses) is that an encryptionalgorithm (cipher) operates on (encrypts) the original data (plaintext)to produce encrypted data (ciphertext), and a corresponding decryptionalgorithm operates on (decrypts) the encrypted data to recover theoriginal data. Keys provide added security by allowing the same cipherto provide different ciphertexts when using different keys. Ciphertextanalysis techniques then apply only to the particular combination ofplaintext, cipher, and key. This helps protect the internal workings ofthe cipher from applications of code-breaking techniques. If aparticular ciphertext is decrypted, a well-designed cipher requires onlya key change to regain its integrity.

The way keys are used divides ciphers into two categories, and theresultant differences often guide the choice of a cipher for aparticular application. An important difference between them is asfollows. Symmetric ciphers use a single key (also called the sharedsecret) for both encryption and decryption, and key modifications duringencryption are therefore easily mirrored in the decryption key.Public-key encryption uses a key pair with public and private keys, andthis makes mirroring key modifications during encryption difficult orimpossible during decryption. Public-key encryption requires morecomputational resources than a symmetric cipher for a given degree ofsecurity. A given key length (e.g., 128 bits) provides a higher degreeof security for a symmetric cipher than for public-key encryption.

Thus, encryption includes knowledge of an encryption algorithm (cipher)and a decryption key. Encryption allows decryption of any messagesencrypted with the corresponding decryption key.

A basic understanding of anonymization is that an original value isirreversibly transformed into a distinguishable but unrecognizablevalue. The technical details underlying the “distinguishable” and“unrecognizable” terms can be complicated. If the resultant value neednot be distinguishable, then the data value may as well be omittedentirely. Recovery of the original value is effected by comparing theanonymized data to that generated by anonymizing known values; when amatch is found, the original value is recovered. Thus, recovery is onlyfeasible when the number of known values to be anonymized and comparedis relatively small when compared to the number of possible inputs. Sometypes of values (such as time stamps) cannot be efficiently anonymizedand these values cannot be anonymized when they have be distinguishableto the receiving party.

Thus, with anonymization there is no decryption key. Anonymizationincludes knowledge of an anonymization algorithm (one-way hashingfunction). Anonymization only allows de-anonymization by comparingcandidate value results. As a result, if there are sufficient candidatevalues, then this problem is not feasible.

An anonymization example in accordance with the present invention is asfollows. In this example, numbers are original values and expectedvalues are from one to ten; words are anonymized values; and the numbern becomes the nth word in a sentence. The anonymization propertiesinclude the anonymization being one-way such that given a word, thenumber cannot be determined without the function (sentence). In thisanonymization example, a hash can be used to anonymize any naturalnumber. However, only ten output values limits the usefulness of thehash.

In a first anonymization example variant, the sentence making up thefunction is “The quick brown fox jumped over the lazy dog again.” Theinput values of one and seven collide on the word “the” in the sentence.Collision for known inputs means that another sentence should be chosenfor the function. In a second anonymization example variant, thesentence making up the function is “The quick brown fox jumped over mylazy dog again.” There are no collisions for expected input values inthis sentence. It can be seen that knowing a word (output) without thefunction (sentence) does not give the input (number).

In sum, an anonymization function is chosen that is one-way such thatknowledge of the result does not reveal the original value. If theanonymization function is known, candidate values must be anonymized andcompared to reveal the original values. This is suitable only when thenumber of candidate values makes this practical. Anonymization is notfor use when there are too many values such that doing a table look-upto determine corresponding values is not feasible. As such,anonymization is not for use with dates/times (e.g., time stamps) havingvarying values. For practical purposes, the anonymization function is ahash function. Otherwise, different types of inputs require differentfunctions. As such, variable inputs are mapped to a fixed number ofoutput values and multiple inputs that map to the same output value are“collisions”. Hash functions should be chosen to minimize the chance ofcollisions. Consequently, a sufficient number of possible inputs greaterthan the expected inputs is required. This assumes that there are manyfewer expected inputs than the possible range of inputs.

As indicated above, the VOD program stream information generated foreach VOD program provided in a stream to a STB in a household 12includes the following fields of information: (i) STB identification,(ii) the date at which the VOD program is provided to the STB, (iii) VODprogram identification, and (iv) VOD program usage information. Cableprovider 14 generates reports of the VOD program stream information forall households. Each record in a report includes the VOD program streaminformation logged for a VOD program provided from cable provider 14 toa STB at a given time. Each record in a report is divided into thefields.

In order for cable provider 14 to provide the VOD program streaminformation for the sampled households to ratings provider 16 withoutknowing the sampled household identities, the VOD program streaminformation reports for all households are anonymized and encrypted inaccordance with the present invention as follows. The STB identificationinformation (i.e., viewer and household identity information includingSTB MAC address and, if used, any account numbers) is anonymized. Thedate information (i.e., the VOD program transaction time stamp) is notanonymized. Otherwise, it would be impractical to control access ofratings provider 16 to sampled households by eligibility time period.

The date information (i.e., the VOD program transaction time stamp) maybe encrypted in order to determine record eligibility separate from theother record information. This would require a different encryption keyto ensure privacy.

All other information including the VOD program identification and theVOD program usage information is encrypted. As such, each viewing recordis encrypted and the encryption key varies by household. The encryptedVOD program identification includes the provider and asset identifiers,and the encrypted VOD program usage information includes aggregateviewing statistics (e.g., total minutes of play, fast forward, rewind).A further improvement is to encrypt those fields billed separately indifferent groups. This requires a different encryption key for eachfield group to ensure privacy. In general, key identifiers (such as STBMAC address) are anonymized, but not encrypted; non-information fieldsto control access filtering may be neither anonymized nor encrypted; andother fields may be partitioned into one or more field groups to beencrypted with their own encryption keys. All transferred records arefurther encrypted between cable provider 14 and ratings provider 16.This includes report and associated data and asset metadata.

With reference to FIG. 2, a walkthrough example of anonymization andencryption performed on a VOD program stream information report inaccordance with the present invention will now be described. In thisexample, the example data fields in the report are as follows: STB MACaddress—one digit; account number—two digits; transaction time stamp—dayto day; provider and asset ID—one letter; aggregate viewingstatistics—totals in minutes. The anonymization function is such thatthe number n means the nth word in the sentence “The quick brown foxjumped over my lazy dog again.” A symmetric cipher is used forencryption such that the encryption key is the decryption key.

FIG. 2 includes a VOD program stream information report 22, a ratingsprovider information table 24, and a cable provider information table26. Report 22 includes the logged VOD program stream informationassociated with all households (sampled and non-sampled) in viewing areaduring a given time period. As described above, this information islogged as VOD programs are streamed to the households. The VOD programstream information for each stream is logged in its own row withinreport 22. As such, each row in report 22 represents a record of VODprogram stream information.

Report 22 represents a format in which VOD program stream information islogged and includes a MAC address (MAC) column 28, a transaction timestamp (Date) column 30, a provider identification (PID) column 32, anasset identification (AID) column 34, a total minutes of play (Play)column 36, a total minutes of fast forward (FF) column 38, and a totalminutes of rewind (Rew) column 40. As shown in FIG. 2, the VOD programstream information for four streams (using the example data fieldsintroduced above) are listed (row-by-row) under the appropriate columnsof report 22. For example, the first record listed in the first row ofreport 22 lists the MAC address as “4”, the date as “6/4”, the PID as“A”, the AID as “F”, the total minutes of Play as “12”, the totalminutes of FF as “0”, and the total minutes of Rew as “0”.

Ratings provider information table 24 includes identificationinformation of the sampled households known by ratings provider 16.Ratings provider 16 uses this information to identify the sampledhouseholds. This information accessible to ratings provider 16 includesthe MAC addresses of STBs in sampled households, account numbersassociated with the sampled households, and the eligibility period inwhich the ratings provider is entitled to access the VOD program streaminformation of the sampled households. The eligibility period isindicative of when a household qualifies as a sampled household asopposed to being a non-sampled household. Accordingly, table 24 includesa MAC address (MAC) column 42, an account (Account) column 44, and aneligibility period (Eligible) column 46. As understood from table 24,the sampled households are those households having STBs with the MACaddress values of “2” and “4”.

Cable provider information table 26 includes identification informationof all households in the viewing area. Cable provider 14 uses thisinformation to identify households which are subscribers of the cableprovider. This information accessible to cable provider 14 includes theMAC address of STBs in households and the account numbers associatedwith the households. Accordingly, table 26 includes a MAC address (MAC)column 48 and an account (Account) column 50.

As mentioned above, ratings provider 16 cannot tell cable provider 14which households are sampled households and the cable provider does nothave access to ratings provider information table 24. Consequently,ratings provider 16 has to acquire an anonymized and encrypted versionof report 22 (which includes information for sampled and non-sampledhouseholds) in order to obtain the information for the sampledhouseholds.

Referring now to FIG. 3, with continual reference to FIG. 2, ananonymized and encrypted version 60 of report 22 in accordance with thepresent invention is shown. Cable provider 14 generates anonymized andencrypted report 60 by anonymizing the MAC address, leaving the Datealone, and encrypting the rest of the VOD program stream information.The rest of the VOD program stream information includes the VOD programidentification (PID and AID) and the VOD program usage information(Play, FF, Rew).

Thus, anonymized and encrypted report 60 includes a MAC′ column 62 whichlists the anonymized MAC addresses. For example, the MAC address valueof “4” of the first and third records in report 22 corresponds to theanonymized MAC address value of “fox” of the first and third records inreport 60; and the MAC address values of “1” and “5” of the second andfourth records in report 22 respectively correspond to the anonymizedMAC address values of “the” and “jumped” of the second and fourthrecords in report 60.

The original MAC addresses are used as the per-record decryption key.Thus, the key value “4” is required to decrypt the encrypted VOD programstream information for the first and third records in report 60; the keyvalue “1” is required to decrypt the encrypted VOD program streaminformation for the second record in report 60; and the key value “5” isrequired to decrypt the encrypted VOD program stream information for thefourth record in report 60.

Ratings provider 16 receives anonymized and encrypted report 60 fromcable provider 14.

Ratings provider 16 knows the anonymization function “The quick brownfox jumped over my lazy dog again” and computes the MAC′ for the sampledhouseholds (i.e., those households having STB MAC address values of “2”and “4”). For example, ratings provider 16 computes the anonmymized MACaddress value of “quick” as the MAC′ value of 2′; and computes theanonymized MAC address value of “fox” as the MAC′ value of 4′.

Referring now to FIG. 4, with continual reference to FIGS. 2 and 3, ade-anonymized and decrypted version 70 of report 60 in accordance withthe present invention is shown. Ratings provider 16 de-anonymizes anddecrypts report 60 to generate the de-anonymized and decrypted report 70by determining that the MAC address value for “fox” is “4”. As such,ratings provider 16 can decrypt records with an anonymized MAC (MAC′)fox. Consequently, ratings provider 16 is able to decrypt the encryptedVOD program stream information of the first record in report 60 as shownin FIG. 4. Ratings provider 16 is unable to decrypt the encrypted VODprogram stream information for the second and fourth records in report60 as these records need respective key values “1” and “5” fordecryption. As indicated above, ratings provider 16 only knows the keyvalues “2” and “4”.

However, ratings provider 16 is able to decrypt the encrypted VODprogram stream information for the third record as the ratings providerknows the required key value “4”. The date associated with the thirdrecord is “6/5”. Referring to ratings provider information table 24 inFIG. 2, ratings provider 16 is only entitled to access the VOD programstream information for MAC address “4” on the date “6/4”. As such, thethird record has an ineligible date and ratings provider 16 is notauthorized to decrypt the information associated with this record eventhough it is able to do so. To this end, ratings provider 16 shouldfilter out records that have ineligible dates (such as the third record)prior to decryption steps being carried out.

Ratings provider 16 cannot decrypt records with a MAC′ other than“quick” or “fox” without trying all possible decryption values. Theproblem with this simple anonymization and encryption approach describedwith reference to FIGS. 3 and 4 is that there are only as many keys asMAC addresses.

This simple anonymization and encryption approach has certain weaknesseswhich may be addressed as follows. A first weakness is thatde-anonymizing compromises encrypted information because thede-anonymized value (MAC address) is the decryption key. A solution isto include external information when forming the decryption key. Thisprotects the decryption key against brute force or dictionary attack.

There are several possibilities for the external information. Theexternal information may include a global shared secret (such as areport key) between cable provider 14 and ratings provider 16. This doesnot protect the decryption key from ratings provider 16, but doesprotect the decryption key from third parties. The external informationmay include information correlated to de-anonymized values not in thereport data. This adds protection from ratings provider 16 as well forunknown values. For example, the external information included may beaccount numbers which are folded into the encryption key to strengthenencryption.

A second weakness with the simple anonymization and encryption approachis that MAC addresses are not diverse. De-anonymizing MAC addresses bybrute force is thus feasible. A solution is to add related information(such as account numbers) known to cable provider 14 and ratingsprovider 16.

In the described simple anonymization and encryption example, there areonly ten possible MAC addresses. However, there are one hundred possibleaccount numbers and MAC addresses are correlated with the accountnumbers. If the combination of MAC address and account number isanonymized, then there are now 1 possible key values to try when usingthe brute force attack. The brute force attack method is now one hundredtimes harder. If the account number is nine digits (as opposed to twodigits), then the brute force attack becomes a billion times harder. Theadvantage to this solution is that an eligible MAC address and itsaccount number are still easily recoverable.

A third weakness with the simple anonymization and encryption approachis that anonymization and encryption is the same across reports.Consequently, cracking a past report assists in cracking a new report. Asolution is to combine data with a value that changes per report.

In sum, the three weaknesses and solutions of the simple anonymizationand encryption approach are as follows. First, de-anonymizingcompromises encrypted information because the de-anonymized value (MACaddress) is the decryption key. The solution to this first weakness isto include external information when forming the decryption key. Second,MAC addresses are not diverse and, consequently, de-anonymizing MACaddresses by brute force or dictionary attack is feasible. The solutionto this second weakness is to add related information known to bothcable provider 14 and ratings provider 16 (e.g., account numbers).Third, anonymization and encryption is the same across reports. As aresult, cracking a past report assists in cracking a new report. Thesolution to this third weakness is to combine data with a value thatchanges per report.

The three solutions are used in accordance with the present invention toprovide a safer anonymization and encryption approach which addressesthe noted weaknesses of the simple anonymization and encryptionapproach. The safer approach includes using a report key (i.e., externalinformation that changes per report) to vary the anonymization andencryption per report. The report key does not appear within the reportin order to protect against de-anonymization from third parties. Thesafer approach also includes using account numbers in the per-recordencryption. As a result, de-anonymizing no longer compromises per-recordencryption unless the corresponding account number is known. Thisprovides for protection against attack on per-record encryption by areceiver.

With reference to FIGS. 5 and 6, a walkthrough example of the saferanonymization and encryption approach performed on a VOD program streaminformation report (such as report 22 shown in FIG. 2) will now bedescribed. In this example, the anonymization function is such thatanonymization is varied using a report key. As such, the numbern.fwdarw.word (n+(report key)). Encryption is carried out using asymmetric cipher (i.e., the encryption key is the decryption key). Inthis example, the report key is a single digit having a value from zeroto nine. The encryption key is not just the MAC address, but includesthe account number and the report key. For example, the encryption keyidentifier value is (10*account number)+(MAC address)+(report key).

As an example, using a report key of seven, cable provider 14 anonymizesand encrypts report 22 to generate a safer anonymized and encryptedreport 80 shown in FIG. 5. Cable provider 14 generates report 80 byanonymizing the MAC address using the report key, leaving the Datealone, and encrypting the rest of the VOD program stream information(i.e., the VOD program identification (PID and AID) and the VOD programusage information (Play, FF, Rew)). Cable provider 14 encrypts the restof the VOD program stream information using an encryption key whichincludes a key identifier value based on the account number, the MACaddress, and the report key.

Thus, report 80 includes a MAC′ column 82 which lists the anonymized MACaddresses. For example, the MAC address of “4” of the first and thirdrecords in report 22 corresponds to the anonymized MAC address of “11”in the first and third records of report 80. This is in accordance withthe anonymization function: MAC address+report key=“4”+“7”=anonymizedMAC address of “11”. The MAC address of “1” of the second record inreport 22 corresponds to the anonymized MAC address of “8” in the secondrecord of report 80 as “1”+“7”=“8”. Likewise, the MAC address of “5” ofthe fourth record in report 22 corresponds to the anonymized MAC addressof “12” in the fourth record of report 80 as “5”+“7”=“12”.

Unlike simple anonymized and encrypted report 60 shown in FIG. 3, theoriginal MAC addresses are not used as the per-record decryption key.Instead, each record of report 80 is encrypted using an encryption keywhich has a key identifier value based on the account number, the MACaddress, and the report key. For example, the VOD program streaminformation of the first record of report 22 is encrypted using theencryption key “891” as this encryption key is (10*account number)+(MACaddress)+(report key)+(10*88)+(4)+(7)=891. Likewise, the VOD programstream information of the second record of report 22 is encrypted usingthe encryption key of “558” (where 10*account number)+(MACaddress)+(report key)=10*55+1+7=558. In this manner, the VOD programstream information of the third and fourth records in report 22 isencrypted using the respective encryption keys of “891” and “1002”.

Thus, ratings provider 16 has to use the decryption keys “891”, “558”,“891”, and “1002” in order to respectively decrypt the encrypted VODprogram stream information of the first, second, third, and fourthrecords of the safer anonymized and encrypted report 80. Ratingsprovider 16 receives report 80 from cable provider 14. Ratings provider16 knows the MAC addresses, the account numbers, and the eligibilityperiods of the sampled households as set forth in table 24 of FIG. 2.Ratings provider 16 also knows the report key (seven in this example),the anonymization function (“the quick brown fox jumped over my lazy dogagain” where the number n word (n+(report key)), and the decryption keygeneration sequence ((10*account number)+(MAC address)+(report key)).However, ratings provider 16 does not know the account numbers forineligible MAC addresses (i.e., the non-sampled households which haveSTB MAC addresses other than “2” and “4”).

Ratings provider 16 can de-anonymize MAC′ address values of “9” and “11”(which respectively correspond to MAC addresses “2” and “4”) and decryptvalues of “689” and “891”. Accordingly, ratings provider 16 is able tode-anonymize and decrypt report 80 to generate a de-anonymized anddecrypted report 90 as shown in FIG. 6. Ratings provider 16 generatesreport 90 by de-anonymizing the MAC′ address value of “11” to generatethe corresponding MAC address value of “4” for the first record ofreport 90. Consequently, ratings provider 16 is able to decrypt theencrypted VOD program stream information of the first record of report90 as shown in FIG. 6 by using the decryption key “891”. Ratingsprovider 16 is unable to decrypt the encrypted VOD program streaminformation for the second and fourth records in report 90 as theserecords respectively require the decryption keys “558” and “1002” fordecryption. As indicated above, ratings provider 16 is only able todetermine the decryption values “689” and “891”.

Again, ratings provider 16 is able to decrypt the encrypted VOD programstream information for the third record as the ratings provider knowsthe required decryption key of “891”. However, as the date associatedwith the third record is “6/5” the third record has an ineligible dateand ratings provider 16 is not authorized to decrypt the informationassociated with this record.

As such, no one can decrypt the encrypted information without using allpossible decryption key values. For the non-sampled households, ratingsprovider 16 does not have the associated account numbers and, thus, theratings provider does not have the decryption keys for the non-sampledhouseholds. Accordingly, ratings provider 16 cannot decrypt theencrypted information associated with the non-sampled households withoutusing all possible decryption key values.

The required knowledge of the safer anonymization and encryptionapproach described with reference to FIGS. 5 and 6 is as follows. Therequired knowledge per report (which is not included within the report)includes the anonymization function, the encryption algorithm (cipher)and key generation function, the field list for anonymization (e.g., keyidentifier=STB MAC address), the field list for encryption (all notneeded for access control filtering), and the report key (best securityif unique for each report). The required knowledge per record in areport includes the key identifier (e.g., the STB MAC address) and theassociated identifier such as an account number (not included within thereport).

In accordance with the present invention, the safer anonymized andencrypted report such as report 80 shown in FIG. 5 is super-encryptedsolely for ratings provider 16. PGP encryption may be used with a publickey exchange requirement. Cable provider 14 and ratings provider 16agree on the report key per report and the report key is to be exchangedas needed. The exchange of a report key from cable provider 14 toratings provider 16 for a report can be done when the cable providerprovides the report to the ratings provider. The report key can beexchanged using a secure protocol such as the Diffie-Hellman exchangeprotocol after the report key has been super-encrypted using PGP. MD5 ispreferably used as the anonymization function such that theanonymization is the MD5 hash of the concatenation of the report key andthe data to be anonymized. Blowfish is preferably used as the encryptionalgorithm with the key length being 128 bits to match the MD5 outputlength. The per-record encryption key is the anonymization of theconcatenation of account number and STB MAC address. In sum, in a reportgenerated using the safer (and simple) anonymization and encryptionapproach, the account numbers do not appear, the STB MAC addresses areanonymized, the transaction time stamps are left alone, and all otherinformation fields are encrypted.

As described, anonymization and encryption is used as the technicalimplementation of privacy concerns for data exchange between cableprovider 14 and ratings provider 16. As described above, the exchangedviewing/usage data is anonymized and encrypted in accordance with thepresent invention as follows.

Report Key

Cable provider 14 and ratings provider 16 coordinate and agree upon ashared secret value (i.e., the report key) for each report. The value ofthe report key is not communicated within the report itself. Maximumprotection is obtained if this value is changed and communicatedsecurely on a per-report basis. Such communications should use securitytechniques such as PGP or authorized Diffie-Hellman key exchange toprotect the exchanged data.

Data Packet Anonymization

For each viewing/usage data packet, the SetTopID element is anonymizedas a one-way hash of the concatenation of the true SetTopID value (e.g.,the STB MAC address) and the report key. This allows recovery of thetrue SetTopID from the anonymized value with knowledge of the reportkey, for known true SetTopID values such as sampled households. The MD5algorithm is recommended as the one-way hash function. Otheralternatives include SHA-1 and related algorithms.

Data Packet Encryption

For each viewing/usage data packet, if anonymized data for non-sampledhouseholds is to be made available for analysis by ratings provider 16,then the data packet type and remaining elements is not encrypted. Thisallows analysis of all data in each report, but only sampled householddata can be correlated across report key changes.

For each viewing/usage data packet, if anonymized data for non-sampledhouseholds is not to be made available for analysis by ratings provider16, then the data packet type and all remaining elements within a datapacket is encrypted with a symmetric cipher using a “row-level” key.This key is formed as a one-way hash of the concatenation of: i) thetrue SetTopID value for the data packet; ii) a value associated with thetrue SetTopID that does not appear in the viewing/usage data, is agreedupon by cable provider 14 and ratings provider 16, and is only known tothe ratings provider for sampled households (account number isrecommended as this associated value because it can be readily collectedfor sampled households); and iii) the report key.

The row-level key can only be reconstructed for sampled households fromthe anonymized and encrypted information. Encrypted non-sampledhousehold data cannot be decrypted and is inaccessible to ratingsprovider 16. Again, MD5 algorithm can be used as the one-way hashfunction and other alternatives include SHA-1 and related algorithms.Blowfish is recommended as the symmetric cipher. Other alternativesinclude Rjindael. The symmetric cipher key length should be chosen tomatch the one-way hash function selected. A subset sample of non-sampledhousehold data can be made available to ratings provider 16 by leavingdata for that subset unencrypted. This allows analysis of unencrypteddata in each report, but only sampled household data can be correlatedacross report key changes. It is noted that reference data remainsunencrypted.

Example XML

An encrypted data packet appears as a <Private> element at the samelevel as the other data packets. Binary values resulting fromanonymization and encryption appear as uppercase hexadecimal digits. Thedata packet type appears within a <Type> sub-element to be encryptedalong with other elements within the data packet. Encrypted elementswithin the encrypted data packet appear within an <Encrypted>sub-element.

e.g., Original Data Packet:

-   <ViewingRecord>-   <Timestamp>2003-01-23T20:55:20.123Z</Timestamp>-   <STB>010203040506</STB>-   <Type>Stream Start</Type>-   <Session>0123456789</Session>-   <Stream>9876543210</Stream>-   <ProviderID>cablelabs-films.com.</ProviderID>-   <AssetID>ABCD1234567890123456</AssetID>-   </ViewingRecord>

After Anonymization:

-   <ViewingRecord>-   <Timestamp>2003-01-23T20:55:20.123Z</Timestamp>-   <STB>1234567890ABCDEF1234567890ABCDEF</STB>-   <Type>Stream Start</Type><Session>0123456789</Session>-   <Stream>9876543210</Stream>-   <ProviderID>cablelabs-films.com</ProviderID>-   <AssetID>ABCD1234567890123456</AssetID>-   </ViewingRecord>

After Encryption:

-   <Private>-   <STB>1234567890ABCDEF1234567890ABCDEF</STB>-   <Encrypted>245624574852342ABF4634734235233DACBE23535</Encrypted>-   </Private>

As can be understood, the <Encrypted>value may require many hexadecimaldigits to represent. In this example XML the timestamp is not being leftunencrypted. For that, the <Private> element would contain a <Timestamp>element.

Data Packet Decryption

A companion decryption process (as described above) is used to undo theanonymization and encryption of applicable data packets as describedabove.

While embodiments of the present invention have been illustrated anddescribed, it is not intended that these embodiments illustrate anddescribe all possible forms of the present invention. Rather, the wordsused in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the present invention.

1. A method comprising: determining, by a computing device and for afirst household that has opted in to monitoring by a ratings provider,first encrypted program usage data by encrypting, using an encryptionkey that corresponds to the first household, first program usage datacorresponding to the first household; determining, by the computingdevice and for a second household that has not opted in to monitoring bythe ratings provider, second encrypted program usage data by anonymizingand encrypting second program usage data corresponding to the secondhousehold; and sending, by the computing device and to the ratingsprovider, the first encrypted program usage data and the secondencrypted program usage data.
 2. The method of claim 1, whereinanonymizing and encrypting the second program usage data comprisesremoving, from the second program usage data, information thatidentifies the second household.
 3. The method of claim 1, wherein thefirst program usage data comprises timing information associated withone or more times when the first household received content.
 4. Themethod of claim 1, wherein the encryption key is based on one or moreof: a shared secret associated with the ratings provider, and an accountnumber associated with the first household.
 5. The method of claim 1,wherein the encryption key comprises a symmetric encryption/decryptionkey.
 6. The method of claim 1, wherein the first program usage datacomprises video on demand usage information.
 7. The method of claim 1,further comprising: receiving, from the ratings provider, an indicationof the first household, wherein determining the first encrypted programusage data is based on the indication of the first household.
 8. Themethod of claim 1, wherein encrypting the first program usage datacomprises anonymizing the first program usage data based, at least inpart, on a shared secret associated with the ratings provider, whereinthe first encrypted program usage data is configured to be de-anonymizedusing the shared secret.
 9. The method of claim 1, wherein the firstencrypted program usage data, when decrypted using the encryption key,identifies the first household.
 10. An apparatus comprising: one or moreprocessors; and memory storing instructions that, when executed by theone or more processors, cause the apparatus to: determine, for a firsthousehold that has opted in to monitoring by a ratings provider, firstencrypted program usage data by encrypting, using an encryption key thatcorresponds to the first household, first program usage datacorresponding to the first household; determine, for a second householdthat has not opted in to monitoring by the ratings provider, secondencrypted program usage data by anonymizing and encrypting secondprogram usage data corresponding to the second household; and send, tothe ratings provider, the first encrypted program usage data and thesecond encrypted program usage data.
 11. The apparatus of claim 10,wherein the instructions, when executed by the one or more processors,cause the apparatus to anonymize and encrypt the second program usagedata by causing the apparatus to remove, from the second program usagedata, information that identifies the second household.
 12. Theapparatus of claim 10, wherein the first program usage data comprisestiming information associated with one or more times when the firsthousehold received content.
 13. The apparatus of claim 10, wherein theencryption key is based on one or more of: a shared secret associatedwith the ratings provider, and an account number associated with thefirst household.
 14. The apparatus of claim 10, wherein the encryptionkey comprises a symmetric encryption/decryption key.
 15. The apparatusof claim 10, wherein the first program usage data comprises video ondemand usage information.
 16. A non-transitory computer-readable mediumstoring instructions that, when executed, cause: determining, for afirst household that has opted in to monitoring by a ratings provider,first encrypted program usage data by encrypting, using an encryptionkey that corresponds to the first household, first program usage datacorresponding to the first household; determining, for a secondhousehold that has not opted in to monitoring by the ratings provider,second encrypted program usage data by anonymizing and encrypting secondprogram usage data corresponding to the second household; and sending,to the ratings provider, the first encrypted program usage data and thesecond encrypted program usage data.
 17. The computer-readable medium ofclaim 16, wherein the first program usage data comprises timinginformation associated with one or more times when the first householdreceived content.
 18. The computer-readable medium of claim 16, whereinthe encryption key is based on one or more of: a shared secretassociated with the ratings provider, and an account number associatedwith the first household.
 19. The computer-readable medium of claim 16,wherein the encryption key comprises a symmetric encryption/decryptionkey.
 20. The computer-readable medium of claim 16, wherein the firstprogram usage data comprises video on demand usage information.